Where does magic come from?
Specifically, in the Warcraft universe, where does it come from? That's actually a complex question, because there are many different kinds of magic practiced in the setting as a whole. We know of the nature magic of the druids and the elemental magic of the shaman (and that these two disparate types of magic often seem to relate to each other while remaining discrete; we know of the fel magic practiced by warlocks and the Burning Legion, and the pure arcane arts of mages. There's also the Holy Light as demonstrated by priests and paladins, the shadowy magics also tapped by some kinds of priests and warlocks as well, and even the raw necromantic power that seems unique to the Scourge, some Forsaken, and death knights. All of these different kinds of magic are magic, and yet each seems to draw from its own source.
Just on Azeroth, we have seen many kinds of magical power and many focusing points, or fonts, of various kinds of power. Several have descended from one another, while still others have intruded due to the interference of various entities. One thing is clear, that there are many paths to power beyond that inherent to the average denizen of the world.
What, therefore, are these sources of magic?